Impact body of a hammer

ABSTRACT

The impact body of a hammer comprises a massive central rod adapted to deliver impacts in operation. The rod has threadedly received thereabout a plurality of weight-adding disc weights, each disc weight being associated with a resilient lock nut positioned behind this disc weight in the direction of the propagation of a compression wave caused by an impact. The lock nut engages the respective one of the disc weights only by the peripheral portion of this lock nut, there being left a gap between the rest of the nut and the disc weight. The lock nut is employed to take up play in the threaded connection between the rod and the disc weight. The impact wave branches off into each of the disc weights and gradually attenuates.

United States Patent Voitsekhovsky et a1. 1

111] 3,823,786 14.51 July 16, 1974 IMPACT BODY OF A HAMMER [76] Inventors: Bogdan Vyacheslavovich Voitsekhovsky, ulitsa Akademicheskaya, 2; Valentin Pavlovich Nikolaev, ulitsa Maltseva, 1, kv. 8; Grigory Yankelevich Shoikhet, ulitsa Pravdy, l, kv. 34, all of Novosibirsk, U.S.S.R.

[22] Filed: May 15, 1973 [21] Appl. No.: 360,477

[52] U.S. C1. 173/126, 175/56 [51] Int. Cl B25d 1/00 [58] Field of Search 173/126, 127, 128, 131, 173/90; 175/56; 299/94 [56] References Cited I UNITED STATES PATENTS 7 v 2,812,745 11/1957 Pyk 173/127 3,245,482 4/1966 Williams etal. 173/126 Primary Examiner-Henry C. Sutherland Assistant Examiner-William F. Pate, lIl Attorney, Agent, or Firm-Eric H. Waters ABSTRACT Thefimpact body of .a hammer comprises a massive central rod adapted to deliver impacts in operation. The rod has threadedly received thereabout a plurality of weight-adding disc weights, each disc weight being associated with a resilient lock nut positioned behind this disc weight in the direction of the propagation of a compression wave caused by an impact.

The lock nut engages the respective one of the disc weights only by the peripheral portion of this lock nut, there being left a gap between the rest of the nut and the disc weight. The lock nut is employed to take up play in the threaded connection between the rod and the disc weight. The impact wave branches off into each of the disc weights and gradually attenuates.

l Claim, 1 Drawing Figure 1 IMPACT BODY OF A HAMMER The present invention relates to improvements in means for working articles by impact or pressure, and, more particularly, it relates to improvements in the impact body of a hammer and can be employed in the structure of heads and rams of various hammers designed for considerable impact force, such as stamping hammers, pile-driving hammers,'rock-crushing hammers, etc.

Widely known in the art is a pile-driving hammer wherein the impact body includes a heavy bottom metal weight. This bottom weight have an upstanding rod attached to the centre thereof, the upper end of the rod being adapted for connection with the lifting rope. The rod receives thereabout a stack of additional metal weights provided each with a'central opening. The same rod also receives thereabout a plurality of relatively thin metal discs made of a deformable and compressable material, the discs being sandwiched between the opposing sides of each adjacent pair of the additional weights and also between the bottom weight and the adjacent additional weight. The above specified known structure is also provided with means for securing the weights and'the discs together, which means permits limited resilient motion of the weights relative to one another.

Following an impact, there propagates itself through the impact body a longitudinal compression wave, the front of the wave being followed by a relatively great compression stress. When the wave reaches the opposite end of the impact body, it is reflected, whereby the rod is subjected to a tensile stress which is substantially equal to the stress developed by the initial compression wave. And, although in this wave process there takes placeattenuation of the amplitude of the tensile wave, the latter is sufficiently strong to induce tensile deformation of the rod carrying the weights. Therefore, the known structure is'lable to fail at hard impacts, i.e., at impacts where the energy of the moving weight is spent over a relatively short path of the travel of the impact body. Quite naturally, the above specified known structure of the impact body is even less adapted for so called dry impacts, i.e., for impacts unaccompanied by plastic deformation, when the kinetic energy of the moving impact body is absorbed by elastic deformation at a mutual impact of a pair of impact bodies, which is the case, e.g., in hammers having a pair of rams moving in opposition to each other.

it is an object of the present invention to step up the strength of an impact body, in order to make the impact body suitable for operation under conditions of hard impacts, even at dry impacts.

This and other objects are attained in an impact body wherein, in accordance with the present invention, the rod and the disc weights are both helically threaded for effecting connection therebetween, and each said disc weight is associated with its individual resilient lock nut which is also threaded onto said rod and which engages its respective disc weight only by the periphery of this lock nut on that side of this disc weight, which is opposite to the side thereof facing the impact end face'of said impact body, there being left between the rest of said lock nut and said respective disc weight a gap of which the value is greater than the value of the play in the threaded connection between said disc weight and said rod.

The herein disclosed impact body has the advantage of being suitable for operation under conditions of harder impacts, even at dry impacts. Moreover, the requirements as to the quality of the materials used for the production of the disc weights becomeless strict, and the disc weights can be made from rolled shapes instead of forgings, as is the case with the disc weights hitherto known.

The'invention will be further described in connection with an embodiment thereof with reference being had to the accompanying drawing illustrating a general view of a part of an impact body, which is partly cut away to display the threaded connection of the disc weight and of the lock nut with the rod.

Referring now in particular to the appended drawing,

the impact body has a centrally located steel rod 1 which-is adapted to deliver impacts in operation by its end face 2. The opposite end of the rod (not shown in the drawing) is employed for attaching the impact body to the rest of the hammer or like structure (not shown in the drawing, either). The central rod 1 carries thereabout a plurality of additional weights 3 in the form of discs with central openings. The rod 1 and the disc weights 3 are provided with external and internal helical threads 4 and 5, respectively, in which way the disc weights are connected with the rod. It is advisable that the shape of the thread should ensure the maximal degree of filling of the sectional area with the material of the connected parts, e.g., by employing metric thread. it is further advisable to employ thread of a special shape, having a reduced profile angle. In short, it is advisable that there should be left minimal gaps and clearances-in the threaded connection. Each one of the disc .weights 3 is associatedwith an individual resilient lock nut 6 which is also provided with an internal thread 8 and thus is threaded onto the rod 1. The provision of the lock nut 6-enables to take up the play in the threaded connection between the respective disc weight and the rod, the lock nut being retained in a desired position in any suitable known manner.

Each one of the lock nuts 6 engages its respective disc weight 3 by its peripheral shoulder on the side of the disc, which is opposite to the side thereof, facing the impact endface 2 of the impact body. Thus, there is left between the rest of the body of the lock nut 6 and its respective disc weight 3 a gap 7 of which the axial extent is greater than the play in the threaded connection of this disc weight 3 with the rod 1, whereby there is ensured independent propagation of the elastic waves from the rod into every one of the disc weights 3. The degree of the elastic deformation of the lock nuts 3 is so selected, that it should be many times greater than the play in the threaded connection between the rod and the respective disc weight.

Let us presume that the impact body of the herein disclosed structure is made to deliver an impact upon a rigid stationary obstacle, and that the speed of the mass of the impact body at the moment of the impact v iS U1.

Then, there is propagated through the rod a longitudinal compression wave resulting in a stress u p r 7P,

The compression wave thus generated, upon having reached the firstone of the disc weights 3, is partly transferred thereto in the form of a shear wave. The stress in the threaded connection attains its maximal value exactly here, in the area of the first disc weight, i.e., of the disc weight 3 which is closest to the impact end face 2. When the compression wave reaches the next successive disc weight, it is already somewhat weakened. Therefore, the stress is at its greatest in the rod and in the disc weights which are nearest to the im- 4 stress 1., is approximately 1.6 greater than the shear stress 1 in the area adjoining the threaded connection.

7 connection. It should be remembered that the further pact end face. Therefore, the necessary strength of I these disc weights can be ensured by appropriate selection of alloy steels as the material of these parts. Those of the disc weights 3 which are remote from the impact end face 2 may be made from steel grades of poorer quality.

The shear stress 1', developed in the disc weights can bec'alculated from the following formula:

1 PUZ where U is the mass propagation speed of the shear wave,

L is the shear (transverse elasticity) modulus of the material of the disc weight.

Taking into consideration that in the area of the threaded connection U U we can find that the shear wave propagates in the body of the disc weight, the weaker it becomes, i.e., the weaker becomes the stress it produces.

What we claim is:

l. The impact body of a hammer, comprising a massive rod provided with a helical thread on the side surface thereof, one of the ends of said rod being adapted to deliver impacts in operation; a plurality of weightadding disc weights also provided with helical thread and coaxially received about said rod, said threads establishing connection between said rod and said disc weights; a plurality of resilient lock nuts, one said lock nut for one said disc weight, said lock nuts being also provided with helical thread and being threadedly received about said rod, each said lock nut engaging the respective one of said disc weights solely by the peripheral portion of said lock nut, on the side of said respective disc weight which is opposite to the side thereof facing said impact end of said rod, so that there is left between the rest of the body of said nut and said respective disc weight a gap which is greater than the value of play in the threaded connection between said disc weight and said rod. 

1. The impact body of a hammer, comprising a massive rod provided with a helical thread on the side surface thereof, one of the ends of said rod being adapted to deliver impacts in operation; a plurality of weight-adding disc weights also provided with helical thread and coaxially received about said rod, said threads establishing connection between said rod and said disc weights; a plurality of resilient lock nuts, one said lock nut for one said disc weight, said lock nuts being also provided with helical thread and being threadedly received about said rod, each said lock nut engaging the respective one of said disc weights solely by the peripheral portion of said lock nut, on the side of said respective disc weight which is opposite to the side thereof facing said impact end of said rod, so that there is left between the rest of the body of said nut and said respective disc weight a gap which is greater than the value of play in the threaded connection between said disc weight and said rod. 